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Date Theme:Webinar 6th May: Kitchen ventilationWebinar 13th May: Ventilation requirements, trends and thermal comfortWebinar 19th May: Moisture control
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Urban Home Ventilation
1
2
Webinar on May 6th,2020 (Urban Home Ventilation part 1: Kitchen Ventilation)• More than 230 people attended
• Recordings now available at: https://www.aivc.org/resources/collection-
publications/events-recordings
Webinar on May 13th,2020 (Urban Home Ventilation part 2: Ventilationrequirements, trends and thermal comfort )• More than 300 people attended
• Recordings now available at: https://www.aivc.org/resources/collection-
publications/events-recordings
webinar2020. 05.19
.
Urban Home Ventilation
Part 3: Moisture control
webinar2020. 05.19
Disclaimer: The sole responsibility for the content of presentations and information given orally during AIVC webinars lies with the authors. It does not necessarily reflect the opinion of AIVC.
Neither AIVC nor the authors are responsible for any use that may be made of information contained therein.
• 15:00 | Welcome, Kari Thunshelle, SINTEF• 15:05 | Strategies for avoiding too high or too low relative humidity in dwellings,
Sverre Holøs, SINTEF, Norway• 15:25 | Moisture buffering in modern timber constructions,
Dimitrios Kraniotis, OsloMet, Norway• 15:45 | Understanding moisture recovery in heat/energy recovery ventilation
as the basis for new market solutions, Peng Liu, SINTEF, Norway• 16:05 | Q&A poll & Workshop discussion, Peter Schild, OsloMet• 16:30 | End of webinar
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Peter Schild
(OsloMet, NO)Kari Thunshelle
(SINEF, NO)
Sverre Holøs
(SINTEF, NO)
Peng Liu
(SINTEF, NO)Dimitrios Kraniotis
(OsloMet, NO)
Valérie Leprince
(INIVE, BE)
Maria Kapsalaki
(INIVE, BE)
Webinar management
webinar2020. 05.19
Urban Home Ventilation Part 3: Moisture control
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webinar2020. 05.19
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How to ask questions during the webinar
Locate the Q&A box (NOT the Chat)
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webinar2020. 05.19
NOTES:
• The webinar presentations will be recorded and published at http://aivc.org/resources/collection-publications/events-recordingswithin a couple of weeks, along with the presentation slides.
• Short Q&A Poll before workshop discussion• After the end of the webinar you will be redirected to our post event survey.
Your feedback is valuable so please take some minutes of your time to fill it in.
www.aivc.org
www.sintef.no
www.oslomet.no/
Facilitated byOrganized by
Urban Home Ventilation
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8
Technology for a better society
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Urban Home Ventilation
The webinar presentations will be recorded and published at http://aivc.org/resources/collection-publications/events-recordings
9
10
Webinar on May 6th,2020 (Urban Home Ventilation part 1: Kitchen Ventilation)• More than 230 people attended
• Recordings now available at: https://www.aivc.org/resources/collection-
publications/events-recordings
Webinar on May 13th,2020 (Urban Home Ventilation part 2: Ventilationrequirements, trends and thermal comfort )• More than 300 people attended
• Recordings now available at: https://www.aivc.org/resources/collection-
publications/events-recordings
webinar2020. 05.19
Healthy Energy-efficient Urban Home Ventilation
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https://www.sintef.no/projectweb/healthy-energy-efficient-urban-home-ventilation/
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Technology for a better society
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STRATEGIES TO AVOID TOO HIGH OR TOO LOW HUMIDITY
Sverre Holøs, SINTEF
Summary. To avoid too low humidity consider:
Action Potential effect Limitations / challenges
Hygroscopic materials Limited Only short-term variation
Decreasing indoor temperature
Limited User comfort and preferences
Adding sources Limited Indoor air quality
Reducing ventilation Moderate Indoor air quality
Recovering moisture Moderate –large
Hygiene and technology, stay tuned...
Humidification Large Energy, hygiene
All above: Condensation risks!
2
1
2
What do we mean by too high or too low indoor moisture?
3https://www.humiditydevices.co.uk/blogs/about-floors/15508913-health-risks-of-adverse-relative-humidity
Arundel & al. reexamined
4
Cases 35 %, controls 26 %(Solomon 1976)
Cases 50 %, controls 43 %(Korsgaard 1982)
??Humidified houses /non-humidified 703/197
(Arlian 1978)
Production?
13 refs on allergic reactions from humidification?
3
4
Relative and absolute moisture, moisture excess, dewpont
5
Absolute humidity: 7 g/kg
Moisture excess: 4 g/kg
Relative humidity 40 %
Tem
per
atu
re °
C
Dew point 9 °C
XXXX 48 %
Causes of building damage -Norway
6
Other causes24%
Rain and snow24%
Moist indoor air
15%
'Construction'6%
Ground water8%
Leakage5%
Several moisture sources
9%
Moisture and other
9%
Data source: SINTEF archives 1993-2002. Bias towards large buildings, non-trivial cases, costly repairs.Bias against single houshold dwellings, "water damage".
Liso, K. R., T. Kvande and J. V. Thue (2006). "Learning from experience - an analysis of process induced building defects in Norway." Research in Building Physics and Building Engineering 2006: 425-432
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Existing buildings are vulnerable to high humidity:
• Cold surfaces, including windows and thermal bridges
• Air leakages
• Cold area (crawl space, garage) ventilated by hot humid outdoor air
• Uncomfortably cold supply air -> low ventilation rates
Moist indoor air15%
8
Compact shape
Heat recoverymechanicalventilation
Efficientlightingand equipment
Demand-controlledventilationand lighting
Well insulated, airtight buildingenvelope with fewthermal bridges
Efficientsunscreen
Thermalstorage
Windows with smallheat loss
Limited windowarea
Newer buildings less vulnerable to high humidity:
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You are not a plant: Relative humidity is not the only important humidity for health and comfort
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Kari at 23 °C, 25 % RH Kari at -6 °C, 80 % RH "Guri" at 23 °C, 25 % RH
What determines indoor humidity?
10
Supply air g/kg
Extract air g/kg
Unknown, CC BY-ND
Buffering
Indoor sources
recycling
Temperature and moisture content
determines RH
Unknown CC BY-SA-NC
Dehumidification
Unknown Author CC BY-SA
Ventilation Rate
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Moisture content of outdoor air – Oslo
11-0.001
0.001
0.003
0.005
0.007
0.009
0.011
0.013
0.015
-20 -15 -10 -5 0 5 10 15 20 25 30 35
kg/k
g
Outdoor temperature (°C)
Indoor Climate 21°C / 40 % RH
Indoor Climate 23°C / 60 % RH
Observations from Blindern, 2010. Data from The Norwegian Meteorological Institute
12
Moisture content of outdoor air
-0.001
0.001
0.003
0.005
0.007
0.009
0.011
0.013
0.015
-20 -15 -10 -5 0 5 10 15 20 25 30 35
kg/k
g
Outdoor temperature (°C)
Oslo
Indoor Climate 21°C / 40 % RH
Indoor Climate 23°C / 60 % RH
-0.001
0.001
0.003
0.005
0.007
0.009
0.011
0.013
0.015
-20 -15 -10 -5 0 5 10 15 20 25 30 35
kg/k
g
Outdoor temperature (°C)
Dublin
Indoor Climate 21°C / 40 % RH,
Indoor Climate 23°C / 60 % RH
-0.001
0.001
0.003
0.005
0.007
0.009
0.011
0.013
0.015
-20 -15 -10 -5 0 5 10 15 20 25 30 35
kg/k
g
Outdoor temperature (°C)
Minsk
Indoor Climate 21°C / 40 % RH
Indoor Climate 23°C / 60 % RH
-0.001
0.001
0.003
0.005
0.007
0.009
0.011
0.013
0.015
-20 -15 -10 -5 0 5 10 15 20 25 30 35
kg/k
g
Outdoor temperature (°C)
Porto
Indoor Climate 21°C / 40 % RH
Indoor Climate 23°C / 60 % RH
Dublin, Minsk and Port climate data from Energy Plus data (ASHRAE)
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What can we do about (too) low humidity
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• Buffering
• Reduce temperature
• Reduce ventilation rates
• Add moisture
• Plants, drying clothes, showering, cooking…
• Room humidifier / airconditioner
• Supply air humidification
• Recover moisture
• Compensating actions
Increased absolute and relative humidity
Increases relative humidity only
Reduces variation only
Does not change humidity
Moisture buffering
14
Effect of materials on diurnal RH variation - laboratory
Photo CC0 Public domain via Piqsels.com
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Moisture buffering: field studies
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Both figs from (Kalamees, et al. 2009)
Kalamees, T., M. Korpi, J. Vinha and J. Kurnitski (2009). "The effects of ventilation systems and building fabric on the stability of indoor temperature and humidity in Finnish detached houses." Building and Environment: 1643-1650.
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Tem
per
atu
re (°
C)
Ab
s. m
ois
ture
(g
wat
er /
kg
dry
air
)
TOOur raw material: outdoor temperature and moisture during one year in Oslo (Blindern)
g/kg 48 h avg moisture weekly avg moisture Weekly avg temp.
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Reducing indoor temperature –low RH
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Absolute humidity: 3,5 g/kg
Moisture excess: 1,5 g/kg
Relative humidity 20 %
Tem
per
atu
re °
C
Dew point -1 °C
XXXX 26 %
Reducing indoor temperatures?
• Generally controlled by inhabitants
• Energy-efficient homes: cheap and easy to heat
• Likely trend: increasing indoor temperatures
18Berge, M. and H. M. Mathisen (2016). "Perceived and measured indoor climate conditions in high-performance residential buildings." Energy and Buildings 127: 1057-1073.
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18
Increasing moisture excess
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Absolute humidity
Moisture excess: 1,5 g/kg
Relative humidity
Tem
per
atu
re °
C
Dew point °C
Increasing excess: reducing ventilation
Indoor RH lowest normally coincides with
• Highly polluted outdoor air
• Freezing risk in heat exchanger
• Peak energy demand
• Spending most of the time indoors
20
Energi i Norge – Wikipedia. Foto Prillen CC BY-SA via Wikimedia Commons
Foto Pixabay, merket fri bruk
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Ventilation and respiration
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• 40-60 g water / hour• 15 liters CO2 /hour• 1 olf
I adult at 23 °C, 1 met, 1 clo
Target 1000 ppm CO2 : 26 m³ / hour per personAdded moisture 1,5-2,3 g / m³
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Ikke-hygroskopisk rotor
Moisture recovery
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Increase excess: adding sources
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0
50
100
150
200
250
300
Potted flower Larger plant Light activity Drying clothes Hard work
Gra
m /
tim
e
Shower 3kg /h Tree 2-4 kg /h
Pin
terest
Pin
terest
Add or remove indoor sources
• Drying of clothes
• Greenery
• Extract at source (shower, cooker, combustion)
• Humidifyer
• Dehumidifier / Air-conditioning
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23
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"Compensating actions"
Against low humidity
• Remove irritant sources (volatiles
and particles)
• Drink
• Select appropriate materials
• Moisten eyes and airways?
25
Against high humidity
• Tighten envelope
• Remove thermal bridges
• (Use robust materials)
Summary:
Action Potential effect Limitations / challenges
Hygroscopic materials Limited Only short-term variation
Decreasing temperature Limited User comfort and preferences
Adding sources Limited Indoor air quality
Reducing ventilation Moderate Indoor air quality
Recovering moisture Moderate – large Stay tuned...
Humidification Large Energy, hygiene
All above: Condensation risks!
26
An integrated approach including Indoor humidity as one parameter of indoor environmental quality, combining elements below
25
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Technology for a better society
28
Target Practical recommenation Significance
Bacteria Avoid growth and reduce dissemination of pathogens
Avoid condensation, keep humidifiers free of bacteria, low RH in heating season
Virus Reduce dissemination of pathogens Avoid extreme highs and lows. Some indications that medium RH may inactivate vira.
Fungi Avoid mould growth on materials -> RH < 85 % on organic materials
Avoid "high" moisture excess: Differs among buildings and climates
Higher in older buildings in cold or humid climates
Mites Reduce population < 40 % RH in bedroom in winter Hard to achieve in warm climates
Respiratory infections For influenza: avoid extreme drop in RH
? Uncertain
Allergic rhinitis & asthma Reduce symptoms Avoid extreme higs and lows Individually high
Chemical interactions ? ? Uncertain
Ozone production ? ? Uncertain
Flooring damage - Select suitable material, avoid extremes Flooring panels according to climatic zone
Dry eyes Reduce symptoms > 40 %, avoid extreme lows Individually high
Skin symptoms Reduce symptoms Avoid extreme lows
Clogged nose Reduce symptoms Avoid extreme lows
Energy demand Avoid unneccesary humidification
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Questions
• Should humidity determine ventilation rate?
• When is it too high?
• When is it too low?
29
More questions
• How much of the day (week, year) are dwellings occupied?
• What is the distribution of ventilation rates, temperatures and
moisture supply? Can the profiles be predicted by dwelling
characteristics?
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Asthma recommendationsOrg rec
National Asthma Council Australia
30-50 %
CDC 35-50 % In hot, humid climates, you may need to use an air conditioner or a dehumidifier or both. Fix water leaks, which allow mold to grow behind walls and under floors.
AAAAI 40-50 % https://www.aaaai.org/conditions-and-treatments/library/allergy-library/humidifiers-and-indoor-allergies
US Housing and Urban Development
30-50% https://www.hud.gov/sites/dfiles/HH/documents/Home%20Assessment%20Checklist%20English.pdf
British Lung Foundation Avoid condensation https://www.blf.org.uk/support-for-you/indoor-air-pollution/improving-air-quality
American Lung Association
To minimize the growth of dust mites, keep your home below 50 percent humidity.
https://www.lung.org/clean-air/at-home/indoor-air-pollutants/dust-mites
NAAF 20-40 % <60 %
Winter in heated roomsSummer
https://www.naaf.no/subsites/fersking---foreldre-og-barn/i-hjemmet/inneklima/luftfuktighet/
Astma allergi Danmark 35-60 %31
Indoor chemistry including ozone
• Catalytic degradation of ozone less efficient at high RH. (Namdari, Lee
et al. 2019)
• There is no certain conclusion about the impact of relative humidity
(RH) on ozone surface removal. According to the previous studies, the
impact of humidity on ozone surface removal generally depended on
the nature of the material surface. (Shen and Gao 2018)
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Influence of temperature and humidity on ozone-surface reactivity is moderate.(Rim, Gall et al. 2016)
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% R
F (g
itt
23 °
C in
ne)
Influensadata: FHI
34
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Tiltak: befuktning
40
Fordampning
Forstøvning
Fig: Qviller klimaprodukter, Stadler Form
Befuktning
• "Uendelig" kapasitet
• Kontrollerbart
• Energikrevende i oppvarmingssituasjon (2,4 kJ/g)
• Hygieniske utfordringer
41
40
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0
1
2
3
4
5
6
7
8
9
10
-25 -15 -5 5 15 25
Fukt
tils
kud
d (g
/m³)
Utetemmperatur (°C)
Fukttilskudd iht NS_EN ISO 13788
Ubrukte bygninger (Hc1) Vanlig bruk (Hc2)
Ukjent bruk (Hc3) Kjøkken m.v. (HC 4)
Svømmehaller o.l. (HC 5)
0
10
20
30
40
50
60
70
-25 -15 -5 5 15 25
% R
F
Utetemperatur (°C)
Innendørs RF etter NS-EN 15026
Low Medium
Effekten av utetemperatur på RF og fukttilskudd
42
Begge figurer (Kalamees, Vinha et al. 2006)
Grunner til å være skeptisk (III)
• Hygieniske utfordringer ved befuktere og
gjenvinnere
• Bakterievekst – Legionella
• Sopp
• Urenheter i vann
• Desinfeksjonsmidler
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"Bypass humidifier" http://www.eiowainspections.com
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43
Grunner til å være skeptisk (IV):Opplevd luftkvalitet påvirkes av temperatur og RF
44
At 12:00
(Mean/median)
At 14:30
(Mean/median)
14 % RF
N=14
24 % RF
N=12
38 % RF
N=12
14 % RF
N=14
24 % RF
N=12
38 % RF
N=12
Dry air* 1.67/0.23 0.09/0 0.06/0 1.95/0.27 1.71/0 0.02/0
Stuffy air* 0.71/0 0.96/0 3.48/1.55 0.43/0 1.33/0 3.22/0.79
Unpleasant odor 0.07/0 1.40/0 1.43/0 0/0 1.72/0 2.34/0
Too cold 2.53/0 1.24/0 1.4/0 2.65/0.73 1.55/0 1.29/0
Too warm 0.34/0 0.61/0 3.32/2.12 0.56/0.08 0.94/0 1.47/0.03
Draught 1.54/0 0.64/0 0.07/0 1.86/0 1.44/0 0.17/0
Varying temperature 1.77/0 1.44/0 2.08/0 1.33/0 1.28/0 1.83/0
Heat from sun 0.18/0 0/0 0/0 0.11/0 0/0 0/0
Lind, Holøs & al. 2018
Foto Kjetil Ree (Own work) [CC BY-SA 3.0 ]
Kari i -6 °C, 80 % RF
Så – hva gjør vi?
• Reduser unødvendig ventilasjon
• Behovsstyring – tomme rom trenger lite luft
• Lavemitterende materialer, innredning og inventar. Fjern kilder heller enn å tynne ut!
• Fuktbufrende materialer i lett møblerte rom
• Unngå overtemperatur
• Styr (også) mot RF. Vurder og kontroller fuktgjenvinning
• Tilfør evt. ekstra fuktighet
• Reduser risiko for bygningsskader
• Bygg tett og velisolert, uten kuldebroer (trykktest og termografer eksisterende bygninger)
• Ha kontroll på trykkforhold
• Ta lav OG høy fuktighet på alvor
45
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Moisture buffering inmodern timber constructions
Dimitrios Kraniotis
Dep. of Civil Engineering & Energy Technology
Oslo Metropolitan University - OsloMet
AIVC – SINTEF Community – OsloMetWorkshop ‘Urban Home Ventilation’ | 19th May 2020
Part 3: Moisture Control
1
Norway: a country with long tradition in timber
2
Photo: Dagfinn Rasmussen, Riksantikvaren Photo: Own archive Photo: Own archive
Photo: Own archive
Increased interest in use of engineered timber products
3
• Tradition is not the only reason• Norway – Strict national framework for energy use in buildings →
dramatic reduction of energy use for heating since 1990 (-69%) (NEA, 2018)• Ensure high indoor environmental quality (IEQ)• Efforts to decrease the carbon footprint from building materials
3
Kathrina Simonen, Life Cycle Assessment
4
Typical light timber construction
SINTEF Community, Byggforskserien
• Interior wooden cladding (softwood)• Thin wooden boards, 12 – 14 mm• Almost always painted
5
Typical light timber construction
SINTEF Community, Byggforskserien
Exterior cladding
Weather resistive barrier (air barrier)
Cavity
Insulating layer
Solid timber
• Solid timber, exposed or covered by gypsum boards• Thick wooden elements, 60 – 140 mm• When exposed, treated with diffusion-open Osmo oil
Modern timber constructionsCross Laminated Timber (CLT)Leading the ‘woodification’ of building industry
6
Asplan Viak, ‘The new Tøyen Swimming Hall’
Glulam from Swedish wood
Laftekompaniet AS
Photo: Own archive
CLTLog
Glulam
SINTEF Community, Byggforskserien
711
Controlling the RH indoors
• DCV - Moisture control, e.g. max at 50%• Humidification / Dehumidification• Adjusting respectively the air temperature indoors• Moisture buffering in hygroscopic surfaces
indoors, building materials, furnitures etc.
8
Moisture buffering – What is it?
Buffer the maxima
Buffer the minima
Moisture buffering of building materials, Rode, Carsten; Peuhkuri, Ruut Hannele; Mortensen, Lone Hedegaard; Hansen, Kurt Kielsgaard; Time, Berit; Gustavsen, Arild; Ojanen, Tuomo; Ahonen, Jarkko; Svennberg, Kaisa; Arfvidsson, Jesperhttps://backend.orbit.dtu.dk/ws/portalfiles/portal/2415500/byg-r126.pdf
NordTest project
• Technical University of Denmark (DTU)• Norwegian Building Research Institute (earlier
NBI, nowadays SINTEF Community);• Technical Research Centre of Finland (VTT);• Lund University, Sweden (LTH);
9
Moisture Buffer Value (MBV)
Moisture Buffer Value:
Moisture buffering of buildingmaterials, Rode, Carsten; Peuhkuri, Ruut Hannele; Mortensen, Lone Hedegaard; Hansen, Kurt Kielsgaard; Time, Berit; Gustavsen, Arild; Ojanen, Tuomo; Ahonen, Jarkko; Svennberg, Kaisa; Arfvidsson, Jesper https://backend.orbit.dtu.dk/ws/portalfiles/portal/2415500/byg-r126.pdf
Internal humidity loads according to ISO 13788
10
max Δv = 4 or 6 g/m3
vi = ve + Δv
Δv = G/V’G: moisture production indoors [g/h]V’: ventilation rate [m3/h]
11
Moisture sources indoors
Branz.co.nz
Moisture buffering and ventilation strategies
12
Photo: thesslagreen.com
Photo: inhabitat.com
What’s the behaviour of CLT under extreme moisture load?
13
Photo: Rumi BaumannDesign: Tron Meyer
Case study 1/4 - Field
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Field test of moisture buffering capacity in CLT modules
Photo: Tormod Aurlien, NMBU
BioKlim field, Ås, NMBUWEEE project - Wood, Energy, Emissions, Experience• Norwegian Institute of Wood Technology• OsloMet (earlier HiOA)• NMBU• Norwegian Institute of Air Research
Test modules:• Volume V = 57 m3
• Exhaust ventilation V’ = 0.5 ACH• Moisture load G = 0.62 kg/h (in total 5.8 kg)
Very high load! (Δv > 20 g/m3)
Moisture buffering, energy potential, and volatile organic compound emissionsof wood exposed to indoor environmentsK. Nore, A.Q. Nyrud, D. Kraniotis, K.R. Skulberg, F. Englund, T. Aurlienhttps://www.tandfonline.com/doi/abs/10.1080/23744731.2017.1288503
outdoors
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Field test of moisture buffering in CLT modules
Moisture buffering, energy potential, and volatile organic compound emissions of wood exposed to indoor environmentsK. Nore, A.Q. Nyrud, D. Kraniotis, K.R. Skulberg, F. Englund, T. Aurlien https://www.tandfonline.com/doi/abs/10.1080/23744731.2017.1288503
Exposed CLTmax RHi ≈ 70%
non-hygroscopicmax RHi ≈ 95%
What is the moisture buffering performance of CLT under controlled operational conditions in the lab?
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Photo: Rumi BaumannDesign: Tron Meyer
Case study 2/4 - Lab
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Moisture buffering capacity of a CLT element
• Step 1: determination of MBV = 1.1 g/(%RH*m2) – almost the same as reportedin NordTest for wooden sample (softwood)
• Step 2: investigation of moisture buffering capacity under ‘operational conditions’• V = 37 m3 | V’ = 57.5 m3/h (= 1.55 ACH = 3.82 m3/h*m2)
‘outdoors’θe ≈ -8.5 °CRHe ≈ 70%
ve = 1.7 g/m3
‘indoors’θe ≈ 21.5 °C
RHi,initial ≈ 20% Vi, initial = 3.5 g/m3
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Moisture buffering capacity of a CLT element
Three different scenarios of moisture load:1. Moisture load,8h = 268.75 g/h
→ expected increase of humidity indoors = 268.75/57.5 = 4.7 g/m3 (RHi ≈ 45%)→ actual increase of humidity indoors = 3.54 g/m3 (RHi ≈ 40%)→ corresponding ‘ventilative’ effect of moisture buffering = 18.4 m3/h (total: 75.9 m3/h)
2. Moisture load,8h = 312.5 g/h→ expected increase of humidity indoors = 312.5/57.5 = 5.4 g/m3 (RHi ≈ 50%)→ actual increase of humidity indoors = 3.7 g/m3 (RHi ≈ 41%)→ corresponding ‘ventilative’ effect of moisture buffering = 27 m3/h (total: 84.5 m3/h)
3. Moisture load,8h = 343.75 g/h → expected increase of humidity indoors = 343.75/57.5 = 6 g/m3 (RHi ≈ 60%)→ actual increase of humidity indoors = 3.8 g/m3 (RHi ≈ 45%)→ corresponding ‘ventilative’ effect of moisture buffering = 33 m3/h (total: 90.5 m3/h)
What is the moisture buffering performance of CLT under fully operational conditions in-situ?
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Photo: Rumi BaumannDesign: Tron Meyer
Case study 3/4 - Field
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Ulsholtveien 31, housing units in exposed CLT
Norwegian Architecture Prize 2017Wooden project of the year 2017
Photo: Are CarlsenDesign: Haugen/Zohar Arkitekter (HZA)
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Ulsholtveien 31, housing units in exposed CLT
• Floor area of the tested appartment, A = 56 m2
• Volume, V = 148 m3
• Decentralised ventilation, V’ = 38 m3/h, in each of the three rooms (2 units in the kitchen/living room (34.4 m2) and 1 unit in each of the two bedrooms (7.3 m2 and 9.7 m2)
• Exhaust ventilation in the bathroom, V’ = 50 m3/h when RHi,bath > 50% or for 15 minutes every 2 hours
Photo: own archive
Photo: own archive
Interior finishing: exposed CLT, treated with diffusion open Osmo oil
bathroom
kitchen/living room
Interior finishing: cement board at the shower
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Ulsholtveien 31, housing units in exposed CLT
Bedroom: 9% < RHi < 54% (too high air temperature, i.e. θi,bed = 29 °C)
Bathroom: 18% < RHi < 66% | water content in wood u = 8.1% - 11.7% < 15.4%
Kitchen/living room: 17% < RHi < 55% | [CO2]: usually below 1150 ppm, max = 1550 ppm
What is the RH indoors in case CLT is replaced by gypsum boards and tiles (bathroom)?
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Photo: Rumi BaumannDesign: Tron Meyer
Case study 4/4 – Simulation
Numerical comparison between gypsum/tiles and CLT
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BedroomCLT
BedroomGypsum board
BathroomCLT + cement board
BathroomTiles
Kitchen/livingroomCLT
Kitchen/livingroom
Gypsum board
RHi, min 9% 6% (-3%) 18% 9% (-9%) 17% 13% (-4%)RHi, max 53% 58% (+5%) 66% 98%
(+32%) 55% 63% (+8%)
Synopsis
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• Under normal moisture loads, the corresponding ventilation effect (maxima of RH) of exposed wooden surfaces in residential buildings can be expected between 20% and 35% (lab investigation).
• In these conditions, the moisture content in CLT is not critical for mould growth, even when CLT exposed in bathrooms (affected by water vapour but not water) and being supported by low-level moisture control (field investigation).
• CLT manages contributes to keep maxima of RH indoors within accepted limits,i.e. < 60% (Category II) (field investigation).
• Overheating has negative consequences not only for the thermal environment but for moisture buffering capacity (minima of RH indoors) as well (field investigation).
• An equivalent apartment in gypsum boards and tiles, instead of CLT, would result to both lower and higher values of RH indoors (field investigation and simulation).
Thank you for your attention!
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UNDERSTANDING MOISTURE RECOVERY IN HEAT/ENERGY RECOVERY VENTILATION AS THE BASIS FOR NEW MARKET SOLUTIONS
Peng Liu, Researcher, SINTEF
Urban Home Ventilation Webinar, 19 May 2020
Three questions
• When does moisture recovery occur?
• What amount of moisture is recovered?
• Is moisture recovery needed?
2
1
2
About/Not about
• Cold period (heating season)
• Air-to-air heat/energy recovery
• Balanced mechanical ventilation
• Well-insulated and air-tight residential buildings
3
Moisture recovery
Moisture recovery rate = internal moisture excess ×moisture recovery efficiency
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3
4
Moisture recovery
Moisture recovery rate = internal moisture excess ×moisture recovery efficiency
5
Internal moisture excess
Difference between indoor and outdoor humidity ratio
• Indoor moisture profile
• Occupants, pets, plants
• Bathing or showering, cooking, dish washing, laundry, drying, cleaning
• Ventilation, building characteristics
• Outdoor moisture
• Weather conditions
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5
6
Internal moisture excess
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Moisture recovery
Moisture recovery rate = internal moisture excess ×moisture recovery efficiency
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7
8
• Two types of air-to-air heat recovery
• Regenerators
• Heat wheel (HRV)
• Enthalpy wheel (ERV)
• Recuperators
• Plate heat exchanger (HRV)
• Membrane energy exchanger (ERV)
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Extract air
Supply air
Exhaust air
Outdoor air
Supply air Outdoor air
Two types of heat/energy recovery ventilator (HRV/ERV) usually applied in residential buildings
Moisture transfer in heat and enthalpy wheels
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Extract air
Supply air
Exhaust air
Outdoor air
9
10
Moisture transfer in heat wheel
Heat wheel surface
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Moisture transfer in heat wheel
Heat wheel surface
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11
12
Moisture transfer in heat wheel
Heat wheel surface
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Heat wheel moisture transfer process for cold climate
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Wet Dry
12
1 2 3
Extract air
Supply air
Exhaust air
Outdoor air
3
3' 3'
Recovered moistureRecovered
moisture
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14
Sorption wheel surface
Moisture transfer in enthalpy wheel
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Enthalpy wheel surface
Sorption wheel surface
Moisture transfer in enthalpy wheel
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Enthalpy wheel surface
15
16
Sorption wheel surface
Moisture transfer in enthalpy wheel
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Enthalpy wheel surface
Enthalpy wheel moisture transfer process for cold climate
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Dry
13
1 3
Extract air
Supply air
Exhaust air
Outdoor air
3' 3'
Recovered moisture
Recovered moisture
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18
Moisture transfer in oxidized or fouled heat wheel
Oxidized or fouled surface
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Moisture transfer in oxidized or fouled heat wheel
Heat wheel surface
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19
20
Moisture transfer in oxidized or fouled heat wheel
Heat wheel surface
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Oxidized or fouled heat wheel moisture transfer process for cold climate
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Wet Dry
12
1 2 3
Extract air
Supply air
Exhaust air
Outdoor air
3
21
22
Moisture transfer in plate and membrane exchangers
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Supply air Outdoor air
Moisture transfer in plate heat exchanger
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Extract airExhaust air
Outdoor airSupply air
Plate (Impermeable to water)
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24
Moisture transfer in plate heat exchanger
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Extract airExhaust air
Outdoor airSupply air
Plate (Impermeable to water)
2
Plate heat exchanger moisture transfer process in HRV/ERV
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Wet Dry
Extract air
Supply airExhaust air
Outdoor air 1
3
1
3
25
26
Moisture transfer in membrane energy exchangers
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Extract airExhaust air
Outdoor airSupply air
Membrane (permeable to water)
Moisture transfer in membrane energy exchangers
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Extract airExhaust air
Outdoor airSupply air
Membrane (permeable to water)
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28
2
Membrane energy exchanger moisture transfer process
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Wet Dry
Extract air
Supply airExhaust air
Outdoor air
3' 3'
Recovered moisture
Recovered moisture
1
3
1
3
Performance of a quasi-counter flow membrane exchanger
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30
Impacts of membrane vs. plate heat exchanger on indoor RH
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RH increase by 7 % with using MEE compared to plate exchanger
RH in range of 30-60 % Plate heat exchanger: 3876 h, 44 % time of the yearMembrane exchanger: 5695 h, 65 % time of the year
0 2000 4000 6000 8000
20
40
60
80
Time (hour)
Ind
oo
r R
H f
or
livin
g ro
om
(%
)
Membrane (heat eff = 80 %, moisture eff = 60 %)
Plate (heat eff = 80 %, moisture eff = 0 %)
A single-family house (two adults and one child) in Oslo
Three questions
• When does moisture recovery occur?
• What amount of moisture is recovered?
• Is moisture recovery needed?
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31
32
Moisture recovery
Moisture recovery rate = internal moisture excess ×moisture recovery efficiency
33
References
• K. M. Smith and S. Svendsen, “The effect of a rotary heat exchanger in room-based ventilation on indoor humidity in existing apartments in
temperate climates,” Energy Build., vol. 116, pp. 349–361, 2016.
• J. Vinha, M. Salminen, K. Salminen, T. Kalamees, J. Kurnitski, and M. Kiviste, “Internal moisture excess of residential buildings in Finland,” J.
Build. Phys., vol. 42, no. 3, pp. 239–258, Nov. 2018.
• S. Geving and J. Holme, “Mean and diurnal indoor air humidity loads in residential buildings,” J. Build. Phys., vol. 35, no. 4, pp. 392–421,
Apr. 2012.
• T. Kalamees, J. Vinha, and J. Kurnitski, “Indoor humidity loads and moisture production in lightweight timber-frame detached houses,” J.
Build. Phys., vol. 29, no. 3, pp. 219–246, 2006.
• T. Kalamees and J. Vinha, “Estonian Climate Analysis for Selecting Moisture Reference Years for Hygrothermal Calculations,” J. Therm. Envel.
Build. Sci., vol. 27, no. 3, pp. 199–220, Jan. 2004.
• P. Liu et al., “A theoretical model to predict frosting limits in cross-flow air-to-air flat plate heat/energy exchangers,” Energy Build., vol. 110,
2016.
• P. Liu, M. Justo Alonso, H. M. Mathisen, and C. Simonson, “Performance of a quasi-counter-flow air-to-air membrane energy exchanger in
cold climates,” Energy Build., vol. 119, 2016.
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Peng Liu
SINTEF Community, Trondheim, Norway
Acknowledgements
Hans Martin Mathisen, NTNU
Anneli Halfvardsson, Flexit
Daniel Nielsen, Flexit
Maria Justo Alonso, NTNU, SINTEF
Projects: EnergiBolig, Defreeze MEE Now, Healthy and Energy
Efficient Urban Home Ventilation
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